linux-kernel - [PATCH 03/11] blkcg: remove unnecessary blkcg_root handling from css

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Date:	Sat, 11 Jul 2015 14:00:46 -0400
From:	Tejun Heo <tj@...nel.org>
To:	axboe@...nel.dk
Cc:	linux-kernel@...r.kernel.org, kernel-team@...com,
	vgoyal@...hat.com, avanzini.arianna@...il.com,
	Tejun Heo <tj@...nel.org>
Subject: [PATCH 03/11] blkcg: remove unnecessary blkcg_root handling from css_alloc/free paths

blkcg_css_alloc() bypasses policy data allocation and blkcg_css_free()
bypasses policy data and blkcg freeing for blkcg_root.  There's no
reason to to treat policy data any differently for blkcg_root.  If the
root css gets allocated after policies are registered, policy
registration path will add policy data; otherwise, the alloc path
will.  The free path isn't never invoked for root csses.

This patch removes the unnecessary special handling of blkcg_root from
css_alloc/free paths.

Signed-off-by: Tejun Heo <tj@...nel.org>
Cc: Vivek Goyal <vgoyal@...hat.com>
---
 block/blk-cgroup.c | 25 ++++++++++---------------
 1 file changed, 10 insertions(+), 15 deletions(-)

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 64cc48f..2a493ce 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -819,18 +819,15 @@ static void blkcg_css_offline(struct cgroup_subsys_state *css)
 static void blkcg_css_free(struct cgroup_subsys_state *css)
 {
 	struct blkcg *blkcg = css_to_blkcg(css);
+	int i;
 
 	mutex_lock(&blkcg_pol_mutex);
 	list_del(&blkcg->all_blkcgs_node);
 	mutex_unlock(&blkcg_pol_mutex);
 
-	if (blkcg != &blkcg_root) {
-		int i;
-
-		for (i = 0; i < BLKCG_MAX_POLS; i++)
-			kfree(blkcg->pd[i]);
-		kfree(blkcg);
-	}
+	for (i = 0; i < BLKCG_MAX_POLS; i++)
+		kfree(blkcg->pd[i]);
+	kfree(blkcg);
 }
 
 static struct cgroup_subsys_state *
@@ -844,13 +841,12 @@ blkcg_css_alloc(struct cgroup_subsys_state *parent_css)
 
 	if (!parent_css) {
 		blkcg = &blkcg_root;
-		goto done;
-	}
-
-	blkcg = kzalloc(sizeof(*blkcg), GFP_KERNEL);
-	if (!blkcg) {
-		ret = ERR_PTR(-ENOMEM);
-		goto free_blkcg;
+	} else {
+		blkcg = kzalloc(sizeof(*blkcg), GFP_KERNEL);
+		if (!blkcg) {
+			ret = ERR_PTR(-ENOMEM);
+			goto free_blkcg;
+		}
 	}
 
 	for (i = 0; i < BLKCG_MAX_POLS ; i++) {
@@ -877,7 +873,6 @@ blkcg_css_alloc(struct cgroup_subsys_state *parent_css)
 		pol->cpd_init_fn(blkcg);
 	}
 
-done:
 	spin_lock_init(&blkcg->lock);
 	INIT_RADIX_TREE(&blkcg->blkg_tree, GFP_NOWAIT);
 	INIT_HLIST_HEAD(&blkcg->blkg_list);
-- 
2.4.3

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